Mut fingerprint id system

ABSTRACT

MEMS ultrasound fingerprint ID systems are provided. Aspects of the systems include the capability of detecting both epidermis and dermis fingerprint patterns in three dimensions. Also provided are methods of making and using the systems, as well as devices that include the systems.

CROSS-REFERENCE TO RELATED APPLICATIONS

Pursuant to 35 U.S.C. §119 (e), this application claims priority to thefiling date of the U.S. Provisional Patent Application Ser. No.61/846,925, filed Jul. 16, 2013; the disclosure of which is hereinincorporated by reference.

INTRODUCTION

Two dimensional fingerprint analysis has been used for centuries forpersonal identification in criminal justice cases. More recently, theapplications for fingerprint identification have been extended to use inthe broader commercial sphere, and have been effectively deployed inniche applications, such as security-critical applications such asbanking.

However, automated optical fingerprint scanning techniques have a numberof limitations that block their use in broader applications. Forexample, automated optical fingerprint scanning techniques sense onlythe epidermal layer of a fingerprint. As a result, they are prone toerrors created by finger contamination.

The marketplace has reflected the limitations of optical fingerprintidentification features for broad market needs, such as personalelectronic devices. While initially provided as features foridentification in many personal electronic devices, optical fingerprintscanners have been removed from most later models due to theselimitations. They lacked the necessary robustness to perform predictablyin such everyday environments.

Ultrasonic fingerprint scanners have been developed in an effort tominimize the limitations of currently available automated opticalfingerprint scanning, and avoid some of the resulting errors, byanalyzing the dermal fingerprint. For example, such a system isdescribed by Schneider, et al. U.S. Pat. No. 5,224,174 issued Jun. 29,1993. However, currently available ultrasonic fingerprint scannersdevices are limited in their applications because of large size, therequirement of a physically moving scanning device, and cost.

Recently, initial experimental work has been conducted on thedevelopment of micromachined ultrasonic transducers (MUTs). Thisresearch includes capacitive micromachined ultrasonic transducers(CMUTs), such as that described at the website produced by placing“http://” before and “.pdf” after“publications.lib.chalmers.se/records/fulltext/166084” (ChalmersUniversity of Technology, Göteborg, Sweden, 2012); and University ofSalerno, Italy, 2011 further described at the website produced byplacing “http://www.” before“sciencedirect.com/science/article/pii/S0924424711005528”. In anadditional line of research, piezoelectric micromachined ultrasonictransducers (PMUTs) have been investigated at the University ofCalifornia, Davis (Thesis, Christine Dempster January, 2013 as furtherdescribed at the website produced by placing “http://” before and“.html” after “gradworks.umi.com/15/30/1530021”.)

It would be a transformative advancement in fingerprint identification(fingerprint ID) if micromachined ultrasonic transducers (MUTs), such ascapacitive micromachined ultrasonic transducers (CMUTs) andpiezoelectric micromachined ultrasonic transducers (PMUTs) could beutilized to accomplish three dimensional fingerprint ID.

SUMMARY

The micromachined ultrasonic transducer fingerprint identificationsystem (MUT fingerprint ID system) of the present invention is arevolutionary advancement in the field of personal authentication. Theunprecedented small size, robust solid-state construction, and orders ofmagnitude lower cost per unit than current systems opens a new era inpersonal identification capabilities, with transformational impact onpersonal electronic devices, many other consumer goods, and entryenablement devices.

The MUT fingerprint ID system is a novel fingerprint sensor based on anarray of ultrasonic transducers. Compared with existing ultrasonicfingerprint sensors based on bulk piezoelectric material, the MUTfingerprint ID system has advantages of a small size, easy fabrication,easy integration with electronics, and fast electronic scanning. Thesefeatures represent a game-changing advancement over currently availablebulky, failure prone mechanical scanners. This novel ultrasonicfingerprint sensor avoids the mechanical scanning needed by earlierultrasonic fingerprint sensors.

Conventional fingerprint sensors used in consumer electronicsapplications are capacitive sensors and are extremely prone to errorsdue to wet, dry or oily fingers. Optical sensors are sensitive to dirton fingers. Unlike both capacitive and optical sensors, which measurethe fingerprint on the epidermis (skin surface), the ultrasonic sensorat the core of the MUT fingerprint ID system can detect the fingerprinton both the epidermis and dermis (subcutaneous) layers.

Since both dermis and epidermis detection are used by MUT fingerprint IDsystem to obtain the correct fingerprint pattern, the sensor isinsensitive to both contamination and moist conditions of fingers. Bycontrast, optical and capacitive sensors are sensitive to contamination.The MUT fingerprint ID system is able to electronically scan the focusedacoustic beam over a large distance (from several mm to several cm) withsmall step size (˜50 μm).

Ultrasonic fingerprint sensors have high fidelity and are used insecurity-critical applications such as banking. However, existingultrasonic sensors use a single bulk ultrasound transducer that ismechanically scanned, making these sensors too large, slow, andexpensive for use in consumer electronics (e.g. laptops andsmartphones).

The novel MUT fingerprint ID system is provided with a micromachinedultrasonic transducer array and a new electronic scanning method that isdigital, has a fast response, and can work in a live scan mode.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a generalized view of the MUT fingerprint ID systemdetecting both epidermis and dermis fingerprint patterns,

FIG. 2 shows the MUT fingerprint ID system phased array embodiment withtransducers subgroup scanning,

FIG. 3 shows a non-beamforming system employing acoustic waveguides todetect both the epidermis and dermis layers,

FIG. 4 shows a cross-section PMUT array embodiment of the MUTfingerprint ID system,

FIG. 5 is a flow diagram showing the fabrication of the MUT fingerprintID system,

FIG. 6 is the system architecture that is particularly useful with CMOS,

FIG. 7 shows the basic ASIC structure of the MUT fingerprint ID system,

FIG. 8 shows the simulated vibration mode-shape of a single PMUT,

FIG. 9 shows the first resonant frequency of a PMUT as a function ofdiameter,

FIG. 10 shows the simulated acoustic beam pattern of PMUT arrays withdifferent pitches,

FIG. 11 shows the experimentally-measured acoustic beam pattern of PMUTarrays with different pitches, and

FIG. 12 shows the experimentally-measured acoustic beam pattern of a15-column PMUT array with 140 micron pitch.

DETAILED DESCRIPTION

The MUT fingerprint ID system of the present invention provides uniquecapabilities to existing personal electronic devices with minimal designmodification, providing a new dimension of capabilities to currentconsumer products. Moreover, the MUT fingerprint ID system is thefoundation for the development of entirely new personal identificationproducts and capabilities.

In contrast to conventional ultrasonic fingerprint sensors based on abulk piezoelectric transducer, the MUT fingerprint ID system hasadvantages of a small size, easy fabrication, and easy integration withelectronics. Moreover, it has a fast response time because of itselectronic scanning feature, replacing prior mechanical scanning.Additionally, the MUT fingerprint ID system features unique engineeringdesigns which solve the near isotropic sound propagation resulting inpoor directivity which have sharply limited the broad application ofprior systems.

The many features of the MUT fingerprint ID system design options worksynergistically to provide the optimum advantages to a specific need.Each option can be selected to work with the greatest advantage to thesystem as a whole, and to its specific application. Thus, while thesefeatures are discussed individually below, with some exampleembodiments, they will be selected or modified by the designing engineerto best accommodate the goals and needs of the complete system, as wellas the devices for which the MUT fingerprint ID system will be afeature.

Before the present invention is described in greater detail, it is to beunderstood that this invention is not limited to particular embodimentsdescribed, as such may, of course, vary. The invention encompassesvarious alternatives, modifications, and equivalents, as will beappreciated by those of skill in the art. It is also to be understoodthat the terminology used herein is for the purpose of describingparticular embodiments only, and is not intended to be limiting, sincethe scope of the present invention will be limited only by the appendedclaims.

Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit unlessthe context clearly dictates otherwise, between the upper and lowerlimit of that range and any other stated or intervening value in thatstated range, is encompassed within the invention. The upper and lowerlimits of these smaller ranges may independently be included in thesmaller ranges and are also encompassed within the invention, subject toany specifically excluded limit in the stated range. Where the statedrange includes one or both of the limits, ranges excluding either orboth of those included limits are also included in the invention.

Certain ranges are presented herein with numerical values being precededby the term “about.” The term “about” is used herein to provide literalsupport for the exact number that it precedes, as well as a number thatis near to or approximately the number that the term precedes. Indetermining whether a number is near to or approximately a specificallyrecited number, the near or approximating unrecited number may be anumber which, in the context in which it is presented, provides thesubstantial equivalent of the specifically recited number.

It is noted that, as used herein and in the appended claims, thesingular forms “a”, “an”, and “the” include plural referents unless thecontext clearly dictates otherwise. It is further noted that the claimscan be drafted to exclude any optional element. As such, this statementis intended to serve as antecedent basis for use of such exclusiveterminology as “solely,” “only” and the like in connection with therecitation of claim elements, or use of a “negative” limitation.

As will be apparent to those of skill in the art upon reading thisdisclosure, each of the individual embodiments described and illustratedherein has discrete components and features which can be readilyseparated from or combined with the features of any of the other severalembodiments without departing from the scope or spirit of the presentinvention. Any recited method can be carried out in the order of eventsrecited or in any other order which is logically possible.

Any publications and patents cited in this specification are hereinincorporated by reference as if each individual publication or patentwere specifically and individually indicated to be incorporated byreference and are incorporated herein by reference to disclose anddescribe the methods and/or materials in connection with which thepublications are cited. The citation of any publication is for itsdisclosure prior to the filing date and should not be construed as anadmission that the present invention is not entitled to antedate suchpublication by virtue of prior invention. Further, the dates ofpublication provided may be different from the actual publication dateswhich may need to be independently confirmed.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. Although any methods andmaterials similar or equivalent to those described herein can also beused in the practice or testing of the present invention, representativeillustrative methods and materials are now described.

Micromachined Ultrasonic Transducer Elements

The MUT fingerprint ID system is distinguished from currently availableultrasonic fingerprint sensors in that it employs in its designmicromachined ultrasonic transducers (MUTs). No MUTs, including CMUTsand PMUTs, have been used for fingerprints sensing beyond preliminaryresearch efforts before the advent of the MUT fingerprint ID system.

Currently, two types of MUTs are generally available, capacitive MUTs(CMUTs) and piezoelectric MUTs (PMUTs). These are described in thespecific examples of the MUT fingerprint ID system provided below.However, other MUTs would also be considered for use in the MUTfingerprint ID system, depending on intended application and otherengineering design considerations.

PMUTs and CMUTs have similar appearances. The basic structure of theCMUT or PMUT is a flexurally-vibrating membrane. By vibrating this smallmembrane, the MUT launches sound.

What differentiates the PMUT and CMUT is that the PMUT is provided witha piezoelectric layer. This piezoelectric layer creates mechanicalmotion in response to applied electric field. By contrast, the CMUT isprovided with two conductive layers. Both the membrane and the fixedcounter-electrode (or wafer) are conductive. Voltage is applied betweenthe membrane and the counter-electrode. This develops an electrostaticforce.

Therefore, the construction of CMUTs and PMUTs is very similar. However,in the case of the PMUT, a piezoelectric layer is provided. In the caseof CMUTs, the piezoelectric layer is absent, but is replaced withoverlapping conductive layers.

CMUTs have been used for a variety of medical and other imagingpurposes. These devices are typically provided through the constructionof arrays of CMUTs, and are operated as arrays. In some instances, thisdetection is accomplished at relatively low frequencies.

For the purposes of the MUT fingerprint ID system, this general type ofultrasonic imaging is conducted at higher frequencies than isconventionally used for medical purposes. The area of medical ultrasoundprovides some clues to optimization of the MUT fingerprint ID system.However, a very different approach, using very high frequencies and veryshort range, is used by the MUT fingerprint ID system.

The MUT fingerprint ID system is distinct from prior medical deviceapplications as it penetrates only a few hundred microns into the tissueinstead of the millimeters or more required by medical devices. Thisallows the MUT fingerprint ID system to provide images of variousstructures both on the surface of the skin and beneath the skin,including the fingerprint image, e.g., in some instances topographicaldetail of a 3D fingerprint.

Directivity

Both CMUTs and PMUTs are micro-electro-mechanical systems (MEMS) devicesmanufactured using semiconductor batch fabrication. Each MUT cantransmit and receive acoustic waves. Acoustic waves are generated asfollows: when a voltage is applied across the bottom and top electrodes,the transducer membrane vibrates, generating an acoustic wave in thesurrounding medium. Conversely, an arriving acoustic wave creates motionin the MUT, producing an electrical signal.

A MUT has a radius a that is small relative to the acoustic wavelengthat which measurements are performed. As a result, the sound spreads inmany directions, i.e. the directivity of an individual MUT is weak. Thischaracteristic has limited the application of these components toproviding fingerprint detection on a broad scale.

The MUT fingerprint ID system has unique engineering design strategiesfor the MEMs structure that solve the directivity problem. As describein more detail in the examples below, the present inventors havedeveloped two specific design strategies to provide directivity. Withthis breakthrough in design strategies, additional variants will bereadily understood by one of ordinary skill in the art.

In one embodiment of the MUT fingerprint ID system, the backside etchingforms a tube which acts as a wave confiner. In this approach, theemitted wave is confined inside the tube rather than propagating in alldirections. As a result, nearly all the acoustic waves confined in thetube propagate to the user's finger directly no matter how large thebeam-width is for the original PMUT.

In another embodiment of the of the MUT fingerprint ID system, a phasedarray of transducers is used to achieve a highly directional, focusedacoustic beam. By appropriately adjusting the phase (delay) of thesignal applied to each channel, the acoustic beam can be focused to adesired depth. For the same focal position, an array with more channelswill focus the acoustic beam to a smaller diameter, but too manychannels will make electronics more complex and expensive.

An alternative way to reduce the focal diameter for an array with agiven number of channels is to increase the pitch between thetransducers in the array, thereby increasing the aperture of the array.For fingerprint sensing, it is desirable to have a focal diameter ofabout 50 μm or less. For a transducer array operating 40 MHz, a6-channel array has a focal diameter below about 50 μm when thetransducer pitch is 150 μm. The fingerprint image is collected byscanning the acoustic beam across the finger.

In some embodiments of the MUT fingerprint ID system, image resolutionis from about 50 μm to 130 μm, specifically about 70 μm to 100 μm, morespecifically about 75 μm to 90 μm, and most specifically about 80 μm.

Bandwidth

MUT fingerprint ID system bandwidth can be optimally selected based onthe intended application, and the particular device configuration, aswill be readily determined by an artisan of ordinary skill. Ranges canbe selected from about 10 MHz to about 100 MHz, specifically from about10 MHz to about 50 MHz, and more specifically from about 10 MHz to about20 MHz.

For currently available transducers, the range of about 10 MHz to about50 MHz is a comfortable design range. However, ranges higher than about100 MHz can be interesting design choices for certain applications. Whenconsidering such alternatives, consideration must be taken to designtransducers that have sufficient signal to noise ratio at frequencies inthis high range. While results can be improved with higher frequencies,upcoming engineering design improvements of transducers will beimportant to accomplish those advantages.

In designing systems, transducers at 100 MHz will produce systems wherethe charge output is substantially smaller. With careful design,transducers that have good signal to noise ratio are possible. Withexpected advances, in the near future devices can be operated in thosehigh ranges. Medical transducer construction and function is instructiveto that end.

Energy & Power Consumption

Many applications of finger print sensors e.g. in battery powereddevices, require ultra-low power dissipation. Fortunately, the MUTfingerprint ID system can be designed to meet this requirement.Specifically, if appropriately designed, the MUT fingerprint ID systemconsumes less than 1 mJ of energy each time a finger print is acquired,with 10 μJ to 500 μJ a more typical range that varies as a function ofsystem parameters such as the resolution of the print (e.g. 500 dpiversus 300 dpi), scheme used (e.g. if phased array beam forming isemployed or not) and fabrication technology.

The frequency at which the MUT fingerprint ID system is used is highlydependent on the application. For example, MUT fingerprint ID systemwhen used in smart phones may be used each time the device is activatedby the user, typically a few times per hour or day. High securityapplications may require frequent re-verification, for example eachminute. Door locks equipped with fingerprint sensors controlling e.g.access to residential homes may be used only a few times per day.

In all cases, to minimize energy consumption the MUT fingerprint IDsystem can be activated only when used. The activation can be controlledfor example with software, by a capacitive sensor, or the MUT arrayitself. In the latter case, only a single or small number of MUTelements are activated periodically, for example ten times per second.Since only a few elements are activated, the power dissipation of thisoperation is very low (typically less than or much less than 1 μWdepending on the design). If a finger or other object is detected, theentire MUT array is activated to acquire a fingerprint pattern. Thanksto the resulting very low average power dissipation the fingerprintsensor can replace the on-switch in many applications such as smartphones: the MUT fingerprint ID system is turned on only when a validfingerprint is recognized with no other steps needed. This mode ofoperation affords maximum convenience and security to the user.

The energy stored in a CR2032 lithium coin cell battery is 2000 to 3000Joules, allowing several million finger print recognitions. If, forexample, the MUT fingerprint ID system is used once per hour, the coincell would last over 40 years if used only for powering the fingerprintID component of the device. Since smart phone batteries have anorder-of-magnitude higher energy capacity, the addition of a MUTfingerprint ID system to such a device would result in negligiblereduction of the running time per battery charge.

To substantiate these figures, some of the present inventors havedeveloped an estimate of the power dissipation below. The actual powerdissipation by a particular implementation will deviate from thisestimate because of variations in the design. Nevertheless, thisestimate provides useful guidance and can easily be adapted to othersituations by anyone skilled in the art.

Consider a fingerprint sensor with a total area of 1 cm by 2 cm.Assuming 500 dpi resolution, this sensor will consist of an array of 200by 400 individual MUTs.

Energy consumption during the transmit phase is dominated by chargingand discharging the capacitance of the MUTs and the electrical wiring.Although this capacitance depends on details of the fabricationtechnology, the capacitance per MUT will typically be less than, andoften much less than 1 pF.

Driving all MUTs with 10V for 4 cycles consumes 16 μJ of energy.Depending on requirements of the application, all transmitters can beactivated at once, or sequentially, or anything in-between. Energyconsumption is independent of the strategy used. In the phased arraymode the energy consumption is higher since several (e.g. 21) MUTs areactivated to sense a single point.

The energy required for reception consists of the energy required foramplifying the signal and the energy required for the analog-to-digitalconversion of the signal. Since the receiver needs to be active for onlya short period after an acoustic pulse has been transmitted, energyconsumption can be reduced drastically by power gating. For example, anacoustic signal traveling 300 μm to 750 μm from the transducer to thedermis and back at a typical sound velocity of 1500 m/s experiences a200 ns to 500 ns delay during most of which the receiving amplifier mustbe ready to accept and amplify the echo.

Assuming 1 mW average power dissipation for an amplifier withapproximately 1 GHz bandwidth, the energy required to process the echoesat all 200 by 400 MUTs is 40 μJ. An 8-Bit analog-to-digital converteroperating at 100 MHz to convert the echo amplitudes to digital signalsconsumes a similar amount of energy.

In summary, the total energy required to transmit, receive, and digitizethe acoustic signals in a 1 cm by 2 cm MUT array is 16 μJ+2×40 μJ orabout 100 μJ if no beam forming is used. With beam forming, the energyis one to two orders of magnitude larger, depending on the number ofMUTs activated per beam.

Additional energy is required to process, identify, and validatefingerprints acquired by the MUT array. The level of energy requireddepends on the processor and the complexity of the algorithms used andfor efficient realizations is typically less than 1 mJ.

Generalized System Design

In the most general case, MUT fingerprint ID sensor generates highlydirectional acoustic pulses, which transmit and reflect at the interfaceof two materials with different acoustic impedance. A coupling materialwith acoustic impedance similar to that of human tissue is filled inbetween the ultrasonic transducers and the top surface of the sensorwhere the user's finger makes contact.

The MUT fingerprint ID system generates highly directional acousticpulses, which transmit and reflect at the interface of two materialswith different acoustic impedance. A coupling material with acousticimpedance similar to that of human tissue is filled between theultrasonic transducers and the top surface of the sensor where theuser's finger makes contact.

The human fingerprint consists of a pattern of ridges and valleys whichhave different acoustic impedance, resulting in measurable differencesin the intensity of the reflected ultrasound. The same pattern ispresent on both the dermis and epidermis: the epidermal reflectionsarrive earlier than the deeper dermal reflections and time-gating can beused to select whether the sensor records the dermal or epidermalfingerprint.

Existing non-ultrasonic fingerprint sensors sense only the epidermalfingerprint and are prone to errors created by dry, wet, dirty or oilyskin. The MUT fingerprint ID system avoids these errors and limitationsby allowing the dermal fingerprint to be measured. Compared withcurrently available ultrasonic fingerprint sensors based on a bulkpiezoelectric transducer, the MUT fingerprint ID system has advantagesof a small size, easy fabrication, easy integration with electronics,and fast response because of electronic scanning instead of mechanicalscanning.

The MUT fingerprint ID system avoids the mechanical scanning needed byearlier ultrasonic fingerprint sensors. One embodiment of the sensor isbased on an array of PMUTs, described below. Alternatively, CMUTs can beused. Both CMUTs and PMUTs are micro-electro-mechanical systems (MEMS)devices manufactured using semiconductor batch fabrication.

Each MUT can transmit and receive acoustic waves. Acoustic waves aregenerated as follows: when a voltage is applied across the bottom andtop electrodes, the transducer membrane vibrates, generating an acousticwave in the surrounding medium. Conversely, an arriving acoustic wavecreates motion in the MUT, producing an electrical signal.

FIG. 1 shows the basic concept of the MUT fingerprint ID system. The MUTfingerprint ID system is designed to detect echoes from the detectorsurface 2, the epidermal layer 23 or the dermal layer 24.

If the epidermal layer 23 has an epidermal ridge 4 that is in contactwith the detector surface 2, providing an epidermis ridge contact point6, there will not be an echo returning from a transmitting wave 15 fromthe detector surface 2 at this point. Thus, where an epidermal ridge 4is in contact with detector surface 2, there will be no (or only a veryweak) echo from that surface.

By contrast, if there is an epidermis valley 8 above the detectorsurface 2, the epidermis valley 8 then contains air. In this case, atransmitting wave 15 will produce a very strong echo wave 16 at the airinterface 10 from the detector surface 2, that is at the surface of theMEMS chip.

The echo wave 16 is produced from the detector surface 2 because theinterface between the air and the coupling material 12 results in astrong acoustic impedance difference at air coupling interface 10. Atthis point, the sound in transmitting wave 14 does not transmit throughthe air in epidermis valley 8. As a result, the transmitting wave 14will bounce off of the detector surface 2 and reflect back as echo wave16. That is the first way the transmitting wave 14 functions within theMUT fingerprint ID system.

An analogy can be drawn from the image from of a photographic camera tothe signal produced by the above transmitting wave 14 reflectingselectively on detector surface 2, resulting in various strengths ofecho wave 16.

There is a very strong echo where there is air above the detectorsurface 2, so this area would look ‘white’ in the image produced,because of the very high signal intensity. By contrast, where anepidermal ridge 4 is in contact with detector surface 2, there will beno echo from that surface, so this area would look ‘black’ as detectedby the ultrasonic transducers 19.

In the intervening spaces between these points, that is the epidermisridge contact point 6 and at the peak of epidermis air couplinginterface 10, the signal would produces many ‘shades of grey’, defininga three dimensional topography of the fingerprint, including many subtleanatomically distinctive features.

The image detected by ultrasonic transducers 19 is then subject tosignal processing in order to produce the three dimensional imagedescribed above. In that image, it would look like epidermis aircoupling interface 10 is an area of high intensity, so it would bebright. By contrast, most of the sound transmits through epidermis ridgecontact point 6. Because most of the sound transmits through the area ofepidermis ridge contact point 6, it will be fairly dark.

The signals detected by the ultrasonic transducers 19 can be sampled byclustering signals from adjoining transducers. By example, ultrasonictransducer cluster 20 can sample a specific area, where singly theywould not receive sufficient signal to provide detection. Similarly,ultrasonic transducer cluster 18 would provide a full survey of the echowave 16 returning directly to them.

In the different embodiments of the MUT fingerprint ID system, thetransducers will receive sound in different ways. However, the importantfeature of the system is the sound's source, that is the way the echo iscoming from the surface interface. Thus, for detecting the epidermis, itis not critical where the transducers are positioned, but rather wherethe reflection happens.

Referring now to the right half of FIG. 1, an additional method forthree dimensional imaging of a fingerprint is provided. In some cases ofpractical usage of the MUT fingerprint ID system, there will becontamination 22, between the finger and the detector surface 2. Byexample, this contamination 22 can be composed of oil, dirt, water, oranything other than air. The contamination 22 may have been on detectorsurface 2 prior to the finger being placed on the surface, or may havebeen on the finger in advance of placement on detector surface 2.

In this case, the sound will pass through the epidermis valley 8containing contamination 22 to reflection interface 27 at dermis layer24. At the adjoining point, the sound will pass through the epidermisridge contact point 6 to reflection interface 25 on the dermis layer 24.As a result, there will be little or no echo produced at the firstinterface with epidermis layer 23. Instead, the sound propagates to thedermal layer 24, and at the dermis point strong or weak echoes will beproduced.

For perspective, the height of the epidermis valley 8 is typically about75-150 μm, more specifically about 100-120 μm. However, because thesedimensions are given by the anatomy, including the air depth of thevalley in the fingertip skin surface, these dimensions are as variableas each individual. The same is true of the actual distance between thedermis and the epidermis, so those distances are given by the humanbody.

The distance between the transducer array and this first surface, thatis coupling material thickness 26, will be selected for the preferredpurpose of the system, but generally can be from about 50 μm-2 mm,specifically from about 50-500 μm, and more specifically about 100-300μm, although it may also be made even smaller, such as about 50-120 μm,and more specifically about 75-100 μm.

The analysis of any propagating acoustic or electromagnetic wave in someinstances includes a far-field and near-field region. While far-fieldimaging is characterized by relatively smooth variations over space, thenear-field regime often exhibits sharp intensity variations, makingimaging difficult. As demonstrated in experiments of the presentinventors, the transducers used in MUT fingerprint ID system are sosmall relative to the operating wavelength that there is no near fieldregion. This fact allows the formation a focused beam very close to thesurface of the MUT array.

FIG. 2 shows another embodiment of the MUT fingerprint ID system whichuses a phased array of transducers to achieve a highly directional,focused acoustic beam. By appropriately adjusting the phase delay of thesignal applied to each channel, the acoustic beam is focused to adesired depth. For the same focal position, an array with more channelsand therefore larger aperture will focus the acoustic beam to a smallerdiameter. However, an array with too many channels will make theelectronics more complex and expensive.

In this embodiment of MUT fingerprint ID system, a phased array oftransducers is used to achieve a highly directional, focused acousticbeam. In this beam-forming approach, while a group of transducers isutilized, not all of the transducers in the array are driven. Instead,smaller groups are driven, by example about 6 to 16 MUTs in a group,such as 10 to 15. However, a narrow focal diameter is achieved byincreasing the aperture of the group by driving every other MUT (therebydoubling the aperture) or every third MUT (thereby tripling theaperture). For example, an array of 6 MUTs operating at 40 MHz has afocal diameter below 50 μm when the transducer pitch is 150 μm,corresponding to an aperture of 750 microns. However, in some instancesit is desirable to have a finer pitch between MUTs for scanningpurposes, as described below. The MUT array can be fabricated with a 50micron pitch, and a 150 micron pitch between the 6 MUTs in the group iscreated by driving every 3^(rd) MUT (MUT #: 1, 4, 7, 10, 13, 16).Alternatively, the array could have 75-micron pitch, in which case thegroup would be formed by driving every other PMUT (MUT #: 1, 3, 5, 7, 9,11).

In a conventional ultrasonic fingerprint scanner, this scanning ismechanical. Here, the novel electronic scanning embodiment of MUTfingerprint ID system is provided where the beam is scanned byincrementally switching from one group of pixels to the next. The pitchbetween each MUT in the array is equal to the step-size of the scanningmotion.

By example, a 50 μm pitch allows the beam to be scanned with a 50 μmstep-size. Meanwhile, as described above, the pitch inside each MUTgroup can be enlarged to obtain a narrow acoustic beam. Finally, both anarrow acoustic beam and a small scanning step can be obtained, whichsubsequently contribute to a high sensing resolution and accuracy.

The beam can be scanned over the full length of the MUT array of the MUTfingerprint ID system, which is about 5-20 mm for a typical fingerprintsensor application. The beam is scanned in two axes using atwo-dimensional array. Alternatively, the finger can be swiped acrossthe array as is done in many capacitive fingerprint sensors. In thelatter case, a smaller number of pixels is needed in the y-axis swipingdirection.

In this embodiment of the MUT fingerprint ID system, the phase of thesignal applied to the y-axis pixels is controlled electronically tofocus the beam in the y-axis, or the focusing can be achieved using acylindrical acoustic focusing lens. A novel means of controlling thephase in the y-axis is to use row-column addressing in which the bottomelectrode of the pixels is patterned and connected on each row. As aresult, the phase delay of the signal is able to be applied to eachchannel, and a small focus area is obtained in both x and y axis.

As shown in FIG. 2, this additional strategy to separate these images isbased on the time of flight of the echoes, and determining which echocomes first. Referring back to FIG. 1, with a short time delay, an echois discernible under epidermis valley 8. The echoes that come from thedermis layer 24 are received later. Because they have to propagatefurther into the tissue, by using time gating, the image to be receivedis selected.

Data is collect for both the epidermis layer 23 and the dermis layer 24of the same finger. This is possible because the dermis image collectedis deeper, with a resulting longer time delay. By contrast, theepidermis image collected is more shallow, as it is on the surface ofthe skin, with a resulting shorter time delay. The image is collectedwith the short time delay recording, but both can be collectedessentially simultaneously.

These two images are fused, providing the best, most accurate, renditionof the fingerprint. Because the two images contain the same information,but may have missing patches, a more complete, combined final data setis obtained from the information gleaned from both data sets

FIG. 2 shows the beam forming design embodiment of the of the MUTfingerprint ID system. This beam forming design was inspired by theanalogous medical imaging area. The configuration has a fairly largearray of MUTs 24. The MUTs are arranged into groups; two groups 26 and28 are illustrated here by way of example. The MUT pitch 30 is thedistance between the adjacent MUTs 24 and is the same as the scanningstep size 32 of the focused acoustic beam 25. When the excitation isswitched from group 26 to group 28, the focused beam undergoesincremental motion with step size 32 equal to the MUT pitch 30. Theintragroup pitch 34 is the pitch between the MUTs within the same group.By way of example, in FIG. 2 the intragroup pitch 34 is equal to fourtimes the MUT pitch 30.

MUT pitch 30 determines scanning step size 32. In some embodiments ofthe MUT fingerprint ID system, the MUT pitch 30 can be from about 10 μmto 130 μm specifically from about 30 μm to 60 μm, and more specificallyfrom about 48 μm to 52 μm. If the step size 32 is 50 μm, thiscorresponds to 500 dpi resolution for fingerprint identification at thecriminal justice requirement level. However, achieving 250 dpiresolution requires only 100 μm step size. The latter level of fidelityis very acceptable for most consumer applications. For clarity, MUTpitch 30 is the spacing between adjacent MUTs 24 in the array, and thespacing between MUTs within the same group is the intragroup pitch 34.

Intragroup pitch 34 and the frequency of the transducer determine thefocus diameter. If the operating frequency is decreased, a largerintragroup pitch 34 is required to keep the same focus diameter. Thefocus diameter determines the lateral resolution of the image, which istypically useful at about 50 μm. Depending on the frequency of thetransducers, a particular group pitch is required to achieve a 50 μmspot size. By example, there can be 11 elements in the group and a 100μm pitch between the elements in the group. Therefore, intragroup pitch34 would be 100 μm.

These MUT fingerprint ID system embodiments can be scaled down whenappropriate to the applications. By example, if the frequency wasdecreased from 40 MHz to 20 MHz, the intragroup pitch 34 would bedoubled from 100 μm to 200 μm to maintain the same focused beamdiameter. This would be the case when keeping the same number ofelements in the group, that is 11. With these teachings of variousembodiments, a practitioner of ordinary skill in the art will adjust thesystem to best advantage for a particular application.

The focus spot is generated by varying the delay by applying a pulsesignal to the transducers. A varying time delay is provided to theelements in the array such that the beam will be focused to a point atthe finger-chip interface. This system provides enough depth of focusthat that focus spot 25 still remains small at the first interface ofthe epidermis and at the deeper interface with the dermis. Once focusspot 25 is focused, it will be remain focused during the scanningprocess. The inventors' research has provided plots that show the depthof focus for a nominal design to be about 1.5 mm, this information isincluded as FIG. 12.

These elements are driven as a phased array, and the beam is formed byappropriately controlling the time delays. All the transducers 24 in thegroup receive the signal. The 11 elements in a group act together toproduce the sound, and those 11 elements detect the echo. This is beamforming and requires the array to work like a phased array.

The output beam can be steered over a range of angles by continuouslyvarying the phase of the drive signals applied to the transducers in agroup. Another strategy is to maintain the focused spot 25 at a pointcentered above the group, as shown in FIG. 2, and do the scanning of thespot by switching from one group to the next group. The transducers canbe used as the system moves from group 1 to group 2 to group 3, and thenback again. The incremental motion of the spot over the array continuesby switching from group to group, allowing advancement of the beam (andthe point where the image is being taken) by the scanning steps 25, 36and 38, etc.

FIG. 3 shows an embodiment of the MUT fingerprint ID system whose coreengineering design is a non-beamforming system employing acoustics. Inthis particular example, piezoelectric micromachined ultrasonictransducers (PMUTs) are utilized. PMUTs, as with other MUTs, have theadvantages of small size, easy fabrication, and easy integration withelectronics.

The PMUT embodiment of the MUT fingerprint ID system achieves a fastresponse time. Because this MUT fingerprint ID system design eliminatesthe need for mechanical scanning, it can function in anelectronically-scanned live scan mode.

The main feature of the PMUT embodiment of the MUT fingerprint ID systemis the use of acoustic wave guides in lieu of, or in some casesaugmented by, electronic phased-array beam focusing approaches. In thisembodiment, an array of PMUTs generates highly directional acousticpulses, which transmit and reflect at the interface of two materialswith different acoustic impedance. A coupling material with acousticimpedance similar to that of human tissue is filled between theultrasonic transducers and the top surface of the sensor where theuser's finger makes contact.

The fingerprint consists of a pattern of ridges and valleys which havedifferent acoustic impedance, resulting in measurable differences in theintensity of the reflected ultrasound. The same pattern is present onboth the dermis and epidermis. The epidermal reflections arrive earlierthan the deeper dermal reflections and timegating can be used to selectwhether the sensor records the dermal or epidermal fingerprint. By thismethod, the PMUT embodiment of the MUT fingerprint ID system avoids ormitigates errors created by finger contamination and dry, wet, dirty, oroily skin, which are the major sources of error in existing optical andcapacitive fingerprint sensors.

In the case of a fine pitch PMUT array (about <50.8 μm), the pitch ofthe PMUT array will typically be smaller than 50.8 μm to achieve a final500 DPI image resolution. This resolution is the rule established by theFBI for an authenticating fingerprint sensor for the purposes ofcriminal investigations.

A large PMUT bandwidth (>10 MHz) can be provided. The height h offingerprint pattern is around 75-150 μm. To avoid overlap betweenacoustic echoes from the dermis layer and epidermis layer, the pulseduration t will typically be smaller than 2 h/c, where c=1500 m/s isacoustic speed in tissue. Consequently, the PMUT bandwidth will normallybe selected at larger than 1/t=10 MHz.

It is often desirable in various embodiments of the MUT fingerprint IDsystem that the PMUT array produces sufficient acoustic output at a lowdrive voltage, ideally less than 10V. The drive voltage can range fromabout 1V to 32V, specifically from about 2V to 15V and more specificallyfrom about 3V to 8V.

In this PMUT embodiment of the MUT fingerprint ID system, the acousticbeamwidth will typically be about <100 μm. The focused acoustic beamsize defines the accuracy of the fingerprint detection. Considering thefingerprint pattern's dimensions (ridge width about 100-300 μm, period˜500 μm), a focus size smaller than about 100 μm is employed torecognize the difference between ridges and valleys.

The concept for the PMUT embodiment of the MUT fingerprint ID system isthat in the case of most currently available ultrasonic transducers, ifa single transducer is utilized, very wide beam width results. In thisembodiment, waveguides 40 are provided to confine an individual PMUTsacoustic output such that a pulse-echo measurement from each PMUT can beconducted individually.

The waveguides 40 function to confine the ultrasonic wave such that itcan only propagate inside the waveguides 40. This makes the beam widthvery small, rather than omnidirectional. Each PMUT transducer 48 actslike an individual pixel of a camera, and takes an isolated image of thetissue contacting the top of its individual waveguide. Each time atransmitting pulse 44 signal is sent from one or several PMUTtransducers 48, each PMUT transducer 48 receives back through couplingmaterial 46 an echo 42 that is predominantly its own.

Within the tube-like waveguides 40 are provided coupling material 46which has the same or similar acoustic impedance as human body tissue.As described below, water or other fluids could be used in thisfunction. However, solids or gels are more suitable in most instances.By example, there are several kinds of Polydimethylsiloxane (PDMS)available which have acoustic impedance suitable for this purpose.

PDMS belongs to a group of polymeric organosilicon compounds that arecommonly referred to as silicones. PDMS is the most widely usedsilicon-based organic polymer, and is particularly known for its unusualrheological (or flow) properties. PDMS is optically clear, and, ingeneral, inert, non-toxic, and non-flammable. It is also calleddimethicone and is one of several types of silicone oil (polymerizedsiloxane). Its current applications include contact lenses and medicaldevices as well as elastomers.

Other materials can be considered for coupling materials. By example,water has impedance sufficiently similar to human tissue that it couldbe employed for this purpose. The difference between the acousticimpedance of water and the human body is very small. However, ingeneral, for most applications, a solid material is a better designchoice than a liquid media for the coupling materials as risks due topotential leakage are minimized. Thus, PDMS is typically more practicalfor these applications.

As a function of waveguide 40, all the transmitting and echo pulses areconfined to this waveguide. Using this design strategy, bothtransmitting pulse 44 and echo pulse 42 will remain within the waveguide40 and not propagate, or have very attenuated propagation, toneighboring ultrasonic transducers 48. As a result, each transducer 48will receive essentially only its own echo pulse 42. The echo time delay50 as determined by comparing the relative echo pulse 42 times from someor all of the transducers 48 is then used to provide a full, threedimensional picture of the fingerprint.

Other parameters of this embodiment are similar to those describe in thegeneral example shown in FIG. 1. For instance, the surface reflectionand the dermis reflection for each pixel. The width of the fingerprintvalley is about 100 μm to 300 μm. Valley range 47 is typically about100-300 μm, representing the pitch of the ridge 49. Typically, afingerprint ridge pitch is about 500 μm.

FIG. 4 shows the basic structure of the PMUT array in the PMUTembodiment of the MUT fingerprint ID system. Each PMUT can transmit andreceive acoustic waves. When a voltage is applied across the bottom andtop electrodes, the transducer membrane vibrates, generating an acousticwave in the surrounding medium. Conversely, an arriving acoustic wavecreates motion in the PMUT, producing an electrical signal. PMUTs withcenter frequency of about >30 MHz and pitch of about <50 μm are usefulranges for some applications.

Simulation results developed by some of the present inventors for PMUTsmade with a layer stack of 2 μm Si and 0.5 μm AIN are listed in Table 1.Since the center frequency scales approximately linearly with thicknessand with the inverse square of diameter, the same frequencies can beachieved in a 5 μm thick membrane by increasing the diameters by 40% to35 μm and 42 μm.

TABLE 1 Simulated PMUT characteristics assuming 2 μm Si and 0.5 μm AINthickness Receiver Center sensitivity Transmit Diameter FrequencyBandwidth S_(R) sensitivity (μm) (MHz) (MHz) (μmV/Pa) S_(T) (kPa/V) Type1 25 46.4 46 0.13 2 Type 2 30 30.5 26 0.21 2

A small driving voltage is desirable for the proposed fingerprint sensorto be used for portable devices. The required drive amplitude isapproximated as follows: over the short (˜100 μm) acoustic path length,absorption and scattering losses are negligible (˜0.5 dB) and thetransmission loss is dominated by the reflection ratio, R, of theselected interface. The epidermis-dermis interface produces a smalleracoustic echo than the epidermis-air interface because the acousticimpedance difference between the dermis and epidermis layers is smaller.

Using 1595 m/s and 1645 m/s as the acoustic velocities in these twolayers, the reflection ratio R will be 0.015. Simulated receiver andtransmit sensitivities are listed in Table 1, SR=0.13 μmV/Pa and ST=2kPa/V, and with a 10V drive input, the expected signal level from thedermis echo is 39 μV. The expected SNR is approximately 15 dB assuming 7μV RMS input-referred noise over a 50 MHz pre-amplifier bandwidth. Thisestimate is conservative: the desired imaging frame rate (<100 fps)means that the actual measurement bandwidth is orders of magnitudesmaller than the bandwidth of the first amplification stage. Inaddition, phased-array techniques using multiple transducers driven inparallel could enable further increases in SNR.

FIG. 4 shows one possible structure for the device depicted in FIG. 3.Here, wafer bonding 52 serves both as a connection and an anchor for thetransducer. The wafer bonding 52 provided on CMOS wafer 54. Thecircuitry for the system is provided within the CMOS wafer 54. The PMUTis located in MEMS wafer 56, typically constructed of silicon.Transducer 58 can be either CMUT or PMUT. The waveguides may be producedby plasma etching tubes into the silicon MEMS wafer. Subsequently,post-fabrication processing is accomplished to fill in the waveguidetubes with PDMS or some other coupling material.

The wafer bonding 52 anchors, and also serve as an electricalconnection, between CMOS wafers 54 and MEMS wafers 56. For each MUTthere will be a top electrode 60 typically constructed of metal. Whenthe transducer is a CMUT, top electrode 60 and bottom electrode 62 areseparated by an air-filled or vacuum-filled gap. FIG. 4 illustrates aPMUT having piezoelectric layer 66 between top electrode 60 and bottomelectrode 62, with passive layer 64 located beneath piezoelectric layer66. The PMUT's membrane structure is driven into vibration by applyingan ac voltage across top electrode 60 and bottom electrode 66, creatingan ultrasound wave that propagates into waveguide 40.

FIG. 5 is a flow diagram of a typical fabrication process for the MUTfingerprint ID system, shown in Steps 1-5. For reference, theorientation shown in FIG. 5 is flipped from that of FIG. 4, with whichit shares many of the same features. This is because this is theorientation during manufacture rather than use.

Step 1 of the fabrication process shows cavity SOI 72 as the basestructure, including cavity 70. This style of wafer can be obtainedpremade from the foundry. In this case, it is termed a cavity SOI.

An alternative approaches is for the cavity to be made as part of theconstruction process, along with the wafer bonding. Components shown ofthe cavity SOI 72 of Step 1 are silicone oxide layer 74, positionedbetween device silicone layer 76 and silicone substrate layer 78.

Step 2 of the fabrication process includes deposition on the surface ofdevice silicone layer 76 of bottom layer 62, typically constructed of(BE) Pt/Ti, and piezoelectric layer 66.

Step 3 of the fabrication process includes via etching 78 ofpiezoelectric layer 66, typically using wet etching, to open bottomelectrode 62.

Step 4 of the fabrication process includes oxide deposition andpatterning of capacitance reducing layer 80 at the edges ofpiezoelectric layer 66. This step is only one more layer, the topelectrode, which is made of patterned materials.

Step 5 of the fabrication process includes aluminum film deposition ofmetal layer 82, forming top electrode 60 and bottom electrode 62. It isimportant to open the layer at this point so that this metal layerconnects to the bottom electrode, becoming part of bottom electrode 62.

FIG. 6 provides a generalized depiction of a system architecture that isparticularly useful in employing CMUT transducers for the MUTfingerprint ID system. However, this structure can also employ PMUTtransducers in some circumstances. The construction of the device inFIG. 6, in contrast to the embodiments shown in FIG. 4, has no cavity.The architecture of the top of both of these device, however, is of asimilar construction.

In common with the prior described embodiments, as shown in FIG. 6, thedesign still includes anchors 52, top electrode 60 and bottom electrode62. However, a vacuum or air-filled gap 70 separates top electrode 60and bottom electrode 62. Shown in the figure is an optional electricalinsulation layer 68 covering top electrode 60. If an ac voltage isapplied between the top and bottom electrode, again this insulationlayer 68 along with the top electrode 60 will start vibrating. Just asin FIG. 4, it will be the active layer vibrating. The insulation layer68 along with the top electrode 60 will also emit an ultrasonic wave. Asa result, these embodiments appear almost the same, however they differin the construction of the MUT. Thus these embodiments achieve the samefunction but with a different approach.

FIG. 7 shows an example electrical control and system of the MUTfingerprint ID system with different phase delays. The PMUT array 71 ispatterned such that all the PMUTs in the same column share the same topelectrodes (blue lines), while every PMUT's bottom electrode connect tolocal pre-amplifier or buffer circuitry 72. This can be done by, forexample, pin-out, wafer bonding between circuit wafer and MEMS wafer, ormonolithic process that enables circuitry and MEMS on a same die.

In transmitting mode, the high voltage driver 73 send out a sequence ofpulses, which could be delay controlled. Meanwhile, the switches 74inside each cell in the array are closed via circuitry. Consequently thePMUT 75 is excited and send out a pulse with delay determined by thephase delay of the applied signal on top electrodes.

For the method 1, no beam-forming is needed, and hence each time only 1of the columns, for example, column j is excited with the high-voltagedriver. Hence all the PMUT on that column will be excited. Whenreceiving the column is selected by circuitry and switch 75 is closedamong all the cells in column j. Hence the signal on PMUT would beamplified and buffered by buffer 76 and directed into data processingunit 77 to provide a fingerprint image. The data processing unit mightcontain necessary data converter, variable gain amplifier, digitalbeamformer, and other hardware to produce fingerprint image.

For beamforming method, different phase delays are applied to differentcolumns to gives X-direction beam-forming as shown in FIG. 2. To performincremental scanning, the delay applied is shifted between high-voltagedriver. The Y-direction beam-forming is done by data processing unitwith the data comes from different rows. The receiving scheme andcontrol is similar to method 1.

MUT Fingerprint ID System Enabled Consumer Products

The MUT fingerprint ID system is ideally suited for incorporation intoexisting consumer product designs, and, in later stage adoption, toenable entirely new products with unique functionality. Theunprecedented small size, robust solid-state construction, and orders ofmagnitude lower cost per unit than current fingerprint ID systems opensa new era in personal identification capabilities, with transformationalimpact on personal electronic devices, many other consumer goods, andentry enablement devices.

Because an ultrasonic wave, unlike its light counterpart, can propagatethrough opaque samples, most materials are ultrasound transparent.Therefore, the MUT fingerprint ID system can enable existing personalelectronic surfaces while still maintaining a standardized appearance.In some cases, the identification surface will be paired with otherfunctional surfaces of the device, such as camera lenses, speakers ormicrophones, to simplify electrical connection to the device circuitry.Internet enabled objects can be provided with authenticated fingerprintsremotely, while others are programmed at the device.

Computer Access Authentication

The MUT fingerprint ID system represents a transformational advancementin e-authentication, and is the successor to computer numeric andalphabetic passcodes. MUT fingerprint ID system will displace computerfile user names, passwords, passcodes, and paraphrases, among others.Besides providing a much higher level of security, the MUT fingerprintID system represents a substantially decreased burden on computer andinternet users.

The MUT fingerprint ID system provides an unprecedented level ofpersonal authentication for on-line and other computer file access.Additionally, consumers will enjoy freedom from the current burdensomesystem of diverse password requirements for the multitude of systems towhich they need access. Because of the fallible nature of passwordsecurity, some systems even require new passwords and complexparaphrases be generated on a regular basis. As a result, many passwordsare actually written and placed on the physical computer, defeating theintent of password secrecy.

The biometric quality of the MUT fingerprint ID system providesauthentication much superior to computer pass codes. Unlike codes whichcan be hacked or taken by trick, such as phishing, the complex, elegantauthentication enabled by the MUT fingerprint ID system is robustlysecure. In contrast to previous fingerprint identification systems, theMUT fingerprint ID system has the capability of analyzing depth andpitch of fingerprint ridges in a clear topographical style map. Also,the ultrasound characteristics of normal dermis and epidermal layers arevery difficult to reproduce in a forgery attempt. Thus, it would behighly difficult, if not impossible, to produce an effective fingerprintforgery for the MUT Fingerprint ID System.

As there are different levels of password complexity appropriate to thesecurity level, graduations of fingerprint authentication allow greaterflexibility of the system to the purpose. Partial fingerprintrecognition, or resolution at a lower level than required for criminallaw identification purposes, can be provided appropriately for many usesof the MUT fingerprint ID system.

Object Free eWallet

Besides computer use applications, during its initial introduction, theMUT Fingerprint ID System will replace pin codes and pass codes incoordination with physical objects, such as bank and credit cards. Asbroader adoption proceeds, the MUT Fingerprint ID System will eliminatethe need for individuals to carry wallets or keys of any type.

In this later stage of the MUT fingerprint ID system adoption,bankcards, credit cards, drivers licenses, passports and other physicalidentification and access devices will be retained in a cloud computerform, and be accessed through the more secure biometric identificationenabled by the MUT fingerprint ID system. Public transportation accesscards will be replaced by a finger touch.

Object Free eKeys

The MUT fingerprint ID system provides, for the first time, thecapability of truly keyless authorized entry. As the MUT fingerprint IDsystem is broadly adopted, entry to one's home and office, as well asentry and operation of one's car, will require no physical “key”, as afinger touch will open this areas to the appropriate persons. Thisunique capability of the MUT fingerprint ID system is particularlyadvantageous in the case of a forgotten, misplaced or stolen wallet orkeys.

The MUT fingerprint ID system eliminates the need of either traditionalmetal or electronic keys. The risk of loss or theft providingunauthorized entry inherent in currently available systems isdramatically reduced or eliminated. For convenience in inclementweather, either gloves providing decloaking of a fingertip, or thin,ultrasound transparency of a glove fingertip can be employed.

In one embodiment of the MUT fingerprint ID system, to gain entry, anauthenticated individual touches an enabled key pad. During earlyadoption, the MUT fingerprint ID system will replace current electronickey pads, initially by retrofitting, and most secured building entrywill be provided in this manner.

In later stages of adoption, entry of an individual into a locked areawill be accomplished simply by grasping the MUT fingerprint ID systemenabled door handle. In this embodiment, the MUT fingerprint ID systemdetection surface can be either embedded into the surface of a standarddoor handle, or covered with a thin layer of decorative metal similar tothat of the body of the handle. However, the detection surface of theMUT fingerprint ID system is so robust to abrasion and weatherchallenges, an overlay of a thin metal veneer or paint would be providedonly for the sake of appearance or preferred texture.

In the case of electronically activated doors, the authenticatedindividual may simply touch the door surface containing a MUTfingerprint ID system key pad to gain entry though electronic dooropening activation. Authorization and entry are provided in a singlemovement, and do not require either a traditional metal key orelectronic key.

The system automatically authenticates the individual when their handgrasps the entry handle, and by the time the handle is turned, the dooris released and is opened. Entry is thus permitted in a single movement.For isolated or late night entry to a building, the reduction of timerequired for entry minimizes risk of criminal activity.

Once the authorized individual has entered a building, interior doorscan be similarly enabled to allow entry. Thus, entry levels to differentrooms within the building can be appropriately assigned. Tradespeople,by example, will have entry authorization to power rooms, cleaningpeople to utility rooms, and executives to specific offices and filerooms. Elevator access to specific floors can be similarly limited toauthorized individuals, when they touch the appropriate elevator buttonfor the correct floor access. Remote authentication can be provided asrequired.

Trusted Individual eKey Authorization

The MUT fingerprint ID system provides a previously unavailable level ofaccess authentication for objects by selected individuals. In the caseof internet enabled objects, entry to trusted individuals is providedremotely, with the option to designate discreet, specific, limitedperiods of time as enabled by the MUT fingerprint ID system.

In some cases, objects to be accessed need not be internet enabled. Inthis case, physical contact is necessary to provide the necessarydirection to the entry feature. This will be the main application in theearly stages of the MUT fingerprint ID system adoption

However, internet enabled objects provide a much broader range ofauthorization capabilities through the MUT fingerprint ID system. Byexample, Tesla cars are internet enabled objects. Going forwards,internet enabled capability will be available in future models of morestandard consumer cars.

Previously, efforts to have similar capabilities for car entry andoperation, such as via a touch to a car door or grasp on a stick shifthandle, have been attempted using visual fingerprint ID technologies.Due to their limitations as discussed previously, they have not enjoyedbroad adoption.

In this embodiment, an access authorizer electronically receivese-fingerprints from trusted individual either directly or via internettransmission. The authorizer can than accept the trusted individual'sfingerprint identification to receive access to an internet enabledobject. The authorized fingerprint is transmitted to the internetenabled object remotely. The trusted individual is thus provided accessat the appropriate level to the internet enabled object. Access can beboth location and time limited.

By example, enabled by the MUT fingerprint ID system, a parent canprovide access to the family car to a teenage offspring for a specificpurpose. The authorization may be to allow chores to be completed duringa specified period. A layered access can be provided, that isauthentication to enter the car and authentication to start the ignitionand drive the car. After the permitted time, the parent enabled accesscan be programmed to lapse. If needed, the offspring can e-request atime extension of the parent. Non-drivers or those who should not drivecould be provided access to the trunk to retrieve personal items,without making the main cab available to them.

Similarly, the MUT fingerprint ID system can allow a property owner toprovide specific tradespeople a time limited, person specific entrycapability in order to complete repair or other tasks during ananticipated period. The preauthorized building entry time can beextended remotely if needed. Alternatively, a broader period for initialentry, with a set period for task completion and later lapse of entrycapability, can be provided. If needed, access can be extended remotely.By example, a delivery person could be provided temporary access to theentry hall of a house to deposit a parcel in a safe manner.

Again, as there are different levels of password complexity appropriateto the security level, gradations of fingerprint authentication allowgreater flexibility of the system to the purpose. Partial fingerprintrecognition, at a lower level than required for criminal lawidentification, can be provided appropriately for many uses of the MUTfingerprint ID system.

Personal Safety Enhancement and Crime Deterrence

Theft of smartphones is now a major concern in cities, by examplerepresenting over half of thefts in San Francisco, Calif., USA. If thesephones could only be used upon the correct fingerprint verification,these crime rates would be reduced by 50%. The MUT fingerprint ID systemenabled smart phones are worthless to a thief, and will reduce crimerates substantially.

In child safety applications, doors to cleaning supplies, medications,and liquor/cigarette cabinets can be MUT fingerprint ID system enabled.In that way, young children are protected from access to dangeroussubstances, and their safety level improved. Through use of the MUTfingerprint ID system, underage family members will be denied access tofamily cigarettes and alcohol supplies.

The MUT fingerprint ID system can be included in the design of digitalgun safes, such as First Alert 6742DF, Fire Resistant Executive GunSafe, Homak Electronic Lock Pistol Box, and Elite Jr. Executive FireResistant Gun Safe, to provide appropriately limited access to firearms.As many firearm deaths are due to children accessing these weapons, theMUT fingerprint ID system will contribute to a lowering of these deaths.Additionally, the MUT fingerprint ID system components will providegreater safeguard against theft, with concomitant decrease ofunregulated criminal use of unregistered firearms.

As firearms are designed as internet enabled objects, the safety aspectof the MUT fingerprint ID system to limit firearm accidents will beextended. Currently, the X system can be included to that end in digitaltrigger locks such as the catmedwid/10000LOCK by Rrarms, among others.As additional internet connectivity is provided to guns, such as theTracking PointXactSystem Precision Guided Firearm, there will be moreopportunities to limit unauthorized use of guns.

The MUT fingerprint ID system can be used as a fail-safe guard bydetecting the identity of the user from a fingerprint on the trigger,locking down the gun from use. In a more traditional use, each gun canbe provided a fingerprint file to identify the user of the gun duringcriminal activity, much as a “black box” is used to gain informationafter an airplane crash.

During periods when an entry door is in an open, unlocked state, the MUTfingerprint ID system can be used to alert the proper authorities andpotential victims when an unauthorized person is entering a building.For example, in domestic violence situations, an abusive spouse under acourt stay-away order can be identified entering a building from theirtouch on the door surface. An e-alert would then be transmitted to thepotential victim and building security in order to notify them to thepossible impending threat. The intruder's position can be tracked thoughthe touch of interior doors. Similarly, in day care facilities,non-custodial family members can be identified at the door, with ane-alert to the possible threat of a child abduction signaled to careproviders.

Enabled Personal Electronic Devices

There are multiple surfaces on personal electronic devices on which theMUT fingerprint ID system sensing surface can be incorporated. The casesof personal electronic devices are excellent locations for the MUTfingerprint ID system sensing surface. These otherwise underutilizedexternal areas of personal electronic devices provide the surfaceavailability key to installation of the MUT fingerprint ID system.

Unlike a camera port, touch keys, view screens, and other personalelectronic interface components, the MUT fingerprint ID system touch padsurface is highly robust to abrasion, fluids, dirt, scratches, and canfunction effectively even through dirt film and other contaminates.Abrasion and scratches from normal use will have little or no effect onfunctionality. The structural integrity of the surface, and its tensilestrength, will avoid compromise of the overall integrity of the devicecasing in which it is located.

To provide some level of protection to the MUT fingerprint ID systemtouch pad, in certain cases this surface may be slightly inwardlyrecessed from the casing's overall surface. In the case where the MUTfingerprint ID system surface is provided a thin esthetic over layer, toblend with the bulk of the casing material, this slight indentation willprovide a cue to the user as to the location of the touch pad.

In many designs, the MUT fingerprint ID system verification will beaccomplished simply by a user picking up the device. As such, thesensing surfaces are usefully located where the device would naturallybe grasped for use. In some cases, this will be the surface the userwould grasp to either open or hold the device.

In the case of personal electronic devices with metal exterior casings,such as currently with the iPad, iMac and other Apple products, the MUTfingerprint ID system can be installed on the surface, and theconnectivity to the control chip accomplished through the electricallyconductive case material. When hard plastic or other non-conductive casematerials are employed in personal electronic device cases, a connectionto the motherboard or internet enabling circuitry will be required, butcan be easily accomplished with co-located surface device features.

Personal electronics represent a wide diversity of products. There arealso crossovers between product types, such as tablets with cellphonecapability, cell phones with large screens which serve as small tablets,Blackberry style capability in both cell phone and tablet formats, etc.Virtually all these products, both when combined in a single device, orwhen provided separately, will enjoy substantial increase in value andversatility when MUT fingerprint ID system is incorporated into theirdesign.

The MUT fingerprint ID system can allow entry into multiple softwarecapabilities and files without the current inconvenience of requiringthe input and recalling multiple passwords, each with their own uniquerequirements for form and complexity. Instead, these systems would enjoya much higher level of authentication without impeding legitimate useraccess to the systems. Currently, software viruses often de-encrypt theusual cumbersome access codes. Thus, both security and ease of use areenabled by the MUT fingerprint ID system.

The MUT fingerprint ID system will be usefully incorporated intostandard cell phones. The MUT fingerprint ID system will also be animportant feature when incorporated into a “smart phone”. Because of MUTfingerprint ID system's small size, very low cost, and robust solidstate construction, it is particularly advantageous for use in smartphones.

The cost of the MUT fingerprint ID system feature will be variabledepending on the application and unit numbers. In some cases, where itis implemented with other device features, its cost will be negligible.In some cases, the cost per unit will be about $0.03 to $2 current US,specifically about $0.05 to $1 current US, and more specifically about$0.10 to $0.50 current US.

Cell Phones

Some examples of currently available, broadly used smart phones whichcould be improved by incorporating the MUT fingerprint ID system areBlackBerry Q10, BlackBerry Z10Sony Xperia Z, Samsung Galaxy Nexus,Samsung Galaxy S3, Samsung Galaxy Note 2, Samsung Galaxy S4, HTC First,HTC Windows Phone 8X, HTC Evo 4G LTE, HTC One X, HTC One X+, HTC DroidDNA; HTC OneApple iPhone 4S, iPhone 5, LG Optimus G, Nexus 4, NokiaLumia 920, Motorola Droid Razr Maxx HD, among others.

Other smart phones which can be modified to include MUT fingerprint IDsystem are Acer Allegro, Acer beTouch E110, Acer beTouch E130, AcerbeTouch E140, Acer DX900, Acer neoTouch, Acer X960, Adaptxt, Android DevPhone, Baidu Yi, BenQ P30, BlackBerry Porsche Design P'9981, BlackBerryTorch, BlackBerry Torch 9800, BlackBerry Charm, BlackBerry Electron,BlackBerry OS, BlackBerry Pearl, BlackBerry Q10, BlackBerry Q5,BlackBerry Quark, BlackBerry Storm, BlackBerry Storm 2, BlackBerryStyle, BlackBerry Tour, BlackBerry Z10, Carrier IQ, Casio G'zOneCommando, Celio Technology Corporation, Comparison of Android devices,Curzon Memories App, CyanogenMod, Dell Streak, Dell Venue Pro, DigitalOcean, Droid Charge, Droid Incredible, Droid Pro, Droid X, FairPhone,Neo 1973, Neo FreeRunner, Find My Phone, Fujitsu Toshiba IS12T, GalaxyNexus, Garmin Nüvifone, GeeksPhoneKeon, GeeksPhone One, GeeksPhone Peak,Genwi, Google Experience device, Google Nexus, Greenphone, H1droid,Helio Ocean, Hiptop Included Software, Hookflash, HP Veer, HTC 7 Mozart,HTC 7 Pro, HTC 7 Surround, HTC 7 Trophy, HTC Advantage X7500, HTCButterfly S, HTC Desire, HTC Desire 600, HTC Desire HD, HTC Desire S,HTC Desire Z, HTC Dream, HTC Explorer, HTC HD7, HTC Hero, HTC Legend,HTC Magic, HTC One, HTC Radar, HTC Raider 4G, HTC Rhyme, HTC Sensation,HTC Sensation XL, HTC Smart, HTC Tattoo, HTC Titan, HTC Titan II, HTCTouch 3G, HTC Touch Viva, HTC Wildfire, HTC Wildfire S, HTC WindowsPhone 8S, HTC Windows Phone 8X, Huawei IDEOS U8150, Huawei Sonic, HuaweiSTREAM X GL07S, Huawei U8230, Huawei U8800, Huawei u8860, I-mate 810-F,IBM Notes Traveler, IBM Simon, Intel AZ210, IOS, IPhone, Iris 3000Videophone, JavaFX Mobile, Jolla (mobile phone), Kyocera 6035, KyoceraEcho, Kyocera Zio, LG enV Touch, LG eXpo, LG GT540, LG GW620, LGIntuition, LG LU2300, LG Optimus 7, LG Optimus Chat, LG Optimus Chic, LGOptimus One, LG Optimus Vu, LG Quantum, LG VS740, LiMo Foundation, LiMoPlatform, Mobilinux, MeeGo, Meizu M8, Meizu M9, Meizu MX, MicromaxCanvas 2 A110, Micromax Canvas 2 Plus A110Q, Micromax Canvas HD A116,Micromax Ninja A89, Momentem, Motodext, Motorola A1000, Motorola A760,Motorola A780, Motorola A910, Motorola A925, Motorola Atrix 2, MotorolaAtrix 4G, Motorola Backflip, Motorola Calgary, Motorola Defy, MotorolaDevour, Motorola Flipout, Motorola i1, Motorola Milestone XT720,Motorola Ming, Motorola Photon, Motorola Photon Q, N-Gage QD, N100(mobile phone), Nexus 4, Nexus One, Nexus S, Ninetology Black Pearl II,Ninetology Insight, Ninetology Outlook Pure, Ninetology Pearl Mini,Ninetology Stealth II, Nirvana Phone, Nokia 3230, Nokia 3250, Nokia3600/3650, Nokia 500, Nokia 5230, Nokia 5250, Nokia 5500 Sport, Nokia5530 XpressMusic, Nokia 5800 XpressMusic, Nokia 603, Nokia 6110Navigator, Nokia 6210 Navigator, Nokia 6290, Nokia 6600, Nokia 6620,Nokia 6630, Nokia 6650 fold, Nokia 6670, Nokia 6680, Nokia 6700 slide,Nokia 6710 Navigator, Nokia 6760 Slide, Nokia 700, Nokia 701, Nokia7610, Nokia 7650, Nokia 7700, Nokia 7710, Nokia 808 PureView, Nokia 9210Communicator, Nokia 9300, Nokia 9500 Communicator, Nokia Asha 302, NokiaAsha 303, Nokia Asha 311, Nokia Asha 501, Nokia C5-00, Nokia C5-03,Nokia C6-01, Nokia C7-00, Nokia Communicator, Nokia E5-00, Nokia E50,Nokia E51, Nokia E52, Nokia E6, Nokia E60, Nokia E63, Nokia E65, NokiaE66, Nokia E7-00, Nokia E70, Nokia E72, Nokia E75, Nokia E90Communicator, Nokia Lumia, Nokia Lumia 620, Nokia Lumia 800, Nokia Lumia810, Nokia Lumia 820, Nokia Lumia 822, Nokia Lumia 900, Nokia Lumia 920,Nokia Lumia 925, Nokia N70, Nokia N71, Nokia N72, Nokia N73, Nokia N75,Nokia N76, Nokia N78, Nokia N79, Nokia N8, Nokia N80, Nokia N81, NokiaN82, Nokia N85, Nokia N86 8MP, Nokia N9, Nokia N90, Nokia N900, NokiaN91, Nokia N92, Nokia N93, Nokia N93i, Nokia N95, Nokia N950, Nokia N96,Nokia N97, Nokia X5, Nuvifone A50, O2 Xda, Ogo (handheld device),OpenEZX, Openmoko Linux, OPhone, Palm (PDA), Palm Centro, Palm Pixi,Palm Pre, Pantech Vega Racer, Pogo Mobile and nVoy, Samsung Ativ S,Samsung B7610, Samsung Behold II, Samsung Focus, Samsung Focus 2,Samsung Focus S, Samsung Galaxy, Samsung Galaxy Ace, Samsung Galaxy AcePlus, Samsung Galaxy Core, Samsung Galaxy Fit, Samsung Galaxy Gio,Samsung Galaxy Mini, Samsung Galaxy Note, Samsung Galaxy Note II,Samsung Galaxy Note III, Samsung Galaxy Pocket, Samsung Galaxy Prevail,Samsung Galaxy S Duos, Samsung Galaxy Y DUOS, Samsung Galaxy Y Pro DUOS,Samsung GT-B7320, Samsung GT-B7330, Samsung i5500, Samsung i5700,Samsung i5800, Samsung i7500, Samsung i8000, Samsung i8910, SamsungMinikit, Samsung Omnia 7, Samsung Omnia W, Samsung Replenish, SamsungSGH-i300, Samsung SGH-i900, Samsung SPH-i300, Samsung SPH-i500, SamsungSPH-M810, Samsung SPH-M900, Samsung Wave 575, Shots On-Line, SiemensSX1, Siemens SX45, Smartphone, Smartphone addiction, Smartphone wars,Soft Input Panel, Sony Ericsson Live with Walkman, Sony Ericsson P1,Sony Ericsson P800, Sony Ericsson P900, Sony Ericsson P910, SonyEricsson P990, Sony Ericsson Satio, Sony Ericsson Vivaz, Sony EricssonXperiaacro, Sony Ericsson Xperia Arc, Sony Ericsson Xperia arc S, SonyEricsson Xperia mini, Sony Ericsson Xperia Mini Pro, Sony EricssonXperia neo, Sony Ericsson Xperia neo V, Sony Ericsson Xperia pro, SonyXperia, Sony Xperia E, Sony Xperia M, Sony Xperia SP, Sony Xperia Z,Sony Xperia ZL, Spice MI-335 (Stellar Craze), Spice Stellar NhanceMi-435, Super LCD, Symbian,T-Mobile myTouch 4G, T-Mobile myTouch 4GSlide, T-Mobile myTouch Q by LG and T-Mobile myTouch by LG, T-MobilePulse, Tizen, Treo 600, Treo 650, Treo 680, Treo 755p, Trium Mondo,Ubuntu Touch, UIQ, Vibo A688, Videophone, Videotelephony, Windows MobileSmartphone, Windows Phone, Xiaomi MI-One, Xiaomi Phone 2, Xiaomi Phone2S, Xplore G18, Xplore M98, and ZTE Tania, amoung others.

Electronic Tablets

The MUT fingerprint ID system has particular advantages as a new featurefor electronic tablets. The MUT fingerprint ID system allows a user easyaccess without having to resort to typing in passcodes. Passcodes havelimitations, such as when a user is on public transportation withconsiderable motion interfering with typing accuracy, or where thedevice needs to be quickly accessed through reentry multiple times.Also, the MUT fingerprint ID system enabled fingerprint verification ofowner identity is an important factor in disincentivizing theft.

Examples of electronic tables which can usefully include MUT fingerprintID system are: iPadApple A4, Apple A5, Apple A5X, Apple A6X and miniApple A5, HP Slate 7 8G Tablet Samsung GALAXY NOTE 8.0, Samsung GALAXYNOTE 10.1 among many others.

The following examples are offered by way of illustration and not by wayof limitation.

EXPERIMENTAL

The 1st order resonant mode of PMUT was obtained by some of the presentinventors by finite element method (FEM) using commercial software(COMSOL).

FIG. 8 shows the finite element analysis simulation of the vibrationmode shape of a PMUT. As seen in FIG. 8 the resonant frequency of PMUT(with layer stack 0.5 μm AIN/2 μm Si and 25 μm diameter) in the air wasabout 64.8 MHz. The resonant frequency is proportional to membranethickness and inversely proportional to membrane diameter squared.

FIG. 9 shows the first resonant frequency of PMUTs as a function ofdiameter (layer stack 0.5 μm AIN/2 μm Si). Higher working frequencygenerates a smaller acoustic wavelength, resulting in a higherresolution fingerprint image.

FIG. 10 shows the simulated acoustic beam pattern of PMUT arrays havingdifferent pitches. Some of the present inventors use a phased array oftransducers to achieve a highly directional, focused acoustic beam, asshown in this figure.

FIG. 11 shows the experimentally measured pressure pattern from a15-column PMUT array. The pressure was measured by scanning a 40 micronhydrophone across the array at a distance of approximately 1.5 mm fromthe array. Measurements were made driving every PMUT (70 micron pitch)and every other PMUT (140 micron pitch).

FIG. 12 shows the experimentally measured pressure pattern from a15-column PMUT array. The pressure was measured by scanning a 40 micronhydrophone across the array in both the x and z (axial) directions. ThePMUTs have a 140 micron pitch and beamforming is used wherein the phaseof each column is controlled to produce a focused acoustic beam.

Although the foregoing invention has been described in some detail byway of illustration and example for purposes of clarity ofunderstanding, it is readily apparent to those of ordinary skill in theart in light of the teachings of this invention that certain changes andmodifications may be made thereto without departing from the spirit orscope of the appended claims.

Accordingly, the preceding merely illustrates the principles of theinvention. It will be appreciated that those skilled in the art will beable to devise various arrangements which, although not explicitlydescribed or shown herein, embody the principles of the invention andare included within its spirit and scope. Furthermore, all examples andconditional language recited herein are principally intended to aid thereader in understanding the principles of the invention and the conceptscontributed by the inventors to furthering the art, and are to beconstrued as being without limitation to such specifically recitedexamples and conditions. Moreover, all statements herein recitingprinciples, aspects, and embodiments of the invention as well asspecific examples thereof, are intended to encompass both structural andfunctional equivalents thereof. Additionally, it is intended that suchequivalents include both currently known equivalents and equivalentsdeveloped in the future, i.e., any elements developed that perform thesame function, regardless of structure. The scope of the presentinvention, therefore, is not intended to be limited to the exemplaryembodiments shown and described herein. Rather, the scope and spirit ofpresent invention is embodied by the appended claims.

1. A MEMS ultrasound fingerprint ID system capable of detecting bothepidermis and dermis fingerprint patterns in three dimensionscomprising: a) a MUT transducer transmitter-receiver array; b) a waveconducting material; c) a wave identifier d) device function circuitry,e) a fingerprint data generator and conveyor.
 2. The MEMS ultrasoundfingerprint ID system of claim 1, wherein said MUT transducertransmitter-receiver array comprises PMUT or CMUT, or a combination ofPMUT and CMUT transducers.
 3. The MEMS ultrasound fingerprint ID systemof claim 1, wherein said wave identifier is selected from a beam formingor echo time of flight system.
 4. The MEMS ultrasound fingerprint IDsystem of claim 1, wherein said system is configured to function in livescan mode.
 5. The MEMS ultrasound fingerprint ID system of claim 1,wherein the image resolution of the fingerprint is from about 50 μm toabout 130 μm.
 6. The MEMS ultrasound fingerprint ID system of claim 5,wherein the image resolution of the fingerprint is from about 70 μm toabout 100 μm.
 7. The MEMS ultrasound fingerprint ID system of claim 6,wherein the image resolution of the fingerprint is from about 75 μm toabout 90 μm.
 8. The MEMS ultrasound fingerprint ID system of claim 1,wherein said wave conducting material is from about 50 μm to about 2 mm.9. The MEMS ultrasound fingerprint ID system of claim 8, wherein saidwave conducting material is from about 75 μm to about 500 μm.
 10. TheMEMS ultrasound fingerprint ID system of claim 9, wherein said waveconducting material is from about 100 μm to about 300 μm.
 11. The MEMSultrasound fingerprint ID system of claim 1, wherein the energy requiredto transmit, receive, and digitize the acoustic signals is from about 50to about 200 μJ.
 12. The MEMS ultrasound fingerprint ID system of claim10, wherein the energy required to transmit, receive, and digitize theacoustic signals is from about 75 to about 150 μJ.
 13. The MEMSultrasound fingerprint ID system of claim 11, wherein the energyrequired to transmit, receive, and digitize the acoustic signals is fromabout 100 μJ to 150 μJ.
 14. The MEMS ultrasound fingerprint ID system ofclaim 1, wherein the drive voltage required for the system is about 1Vto about 50V.
 15. The MEMS ultrasound fingerprint ID system of claim 13,wherein drive voltage required for the system is about 3V to about 40V.16. The MEMS ultrasound fingerprint ID system of claim 13, wherein drivevoltage required for the system is about 24V to about 30V.
 17. The MEMSultrasound fingerprint ID system of claim 1, wherein each MUT is coupledto an acoustic waveguide that is configured to confine the ultrasoundemanating from and returning to the MUT.
 18. The MEMS ultrasoundfingerprint ID system of claim 1, wherein the system is configured todrive the MUTs in groups and the acoustic beam is scanned by switchingthe excitation from group to group in sequence.
 19. A personal electricdevice comprising the MEMS ultrasound fingerprint ID system of claim 1.20. An internet enabled object comprising the MEMS ultrasoundfingerprint ID system of claim
 1. 21. An entry enablement devicecomprising the MEMS ultrasound fingerprint ID system of claim 1.